Buckle folding unit and sheet-fed folding machine including the buckle folding unit

ABSTRACT

A buckle folding unit for sheets includes a buckle plate, three rollers that form a transport roller pair and a folding roller pair, and a blown-air nozzle for guiding the sheets. The at least one blown-air nozzle emits a blown-air jet in a direction radial to a common roller of the transport roller pair and the folding roller pair. The air jet places the sheet against the surface of the common roller and guides it into a nip of the folding roller pair in a defined way, advantageously resulting in an improved quality of the fold. A sheet-fed folding machine including a buckle folding unit is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2015 213 334.6, filed Jul. 16, 2015; the prior application is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a buckle folding unit for sheet-shaped elements. The buckle folding unit includes a buckle plate, three rollers forming a transport roller pair for feeding the sheet-shaped elements and a folding roller pair for folding the sheet-shaped elements, and at least one blown-air nozzle for guiding the sheet-shaped elements. The invention also relates to a sheet-fed folding machine that includes such a buckle folding unit.

Buckle folding machines and knife folding machines are known in the art. If buckle folding units and knife folding units are combined in one machine, it is known as a combination folding machine. Buckle folding units create parallel folds and downstream knife folding units create cross folds.

In buckle folding machines, a sheet is transported in a direction of transport, passing through at least the following units: a feeder, a transfer table, a buckle folding unit and a delivery.

The construction of a buckle folding machine including a plurality of buckle folding units is disclosed in German Patent Application DE 10 2004 041 471 A1. A respective buckle folding unit is formed of a buckle plate and three folding rollers disposed in two folding roller pairs.

It is known in the art to use air nozzles in buckle plates. The air nozzles are intended to assist in a reliable, accurate transportation of sheets. European Patent EP 1 577 244 B1, corresponding to U.S. Patent Application Publication US 2005/0209079, proposes the use of blown-air nozzles in a buckle plate, in which the blown-air nozzles are disposed in an upper sheet-guiding device immediately downstream of the upper entrance to the buckle plate. The blown-air nozzles are provided with the intention of creating an air jet extending substantially in the direction of introduction of the buckle plate, assisting in the introduction of a sheet until the leading edge of the sheet rests against the buckle plate stop. In one possible embodiment, the blown-air nozzles are embodied as Venturi nozzles.

The use of blown-air nozzles in buckle folding units is also described in German Utility Model DE 89 06 505 U1, in U.S. Pat. No. 2,699,331, and in German Utility Model DE 7029693 U1. The latter discloses a gate fold unit and a center fold unit for implementing gate folds and center folds. The job of the blown-air nozzle, which operates with compressed air, is to ensure that a folded product that has been created in a first folding unit and already has a fold safely enters the buckle plate of a second buckle folding unit. In one embodiment, the blown-air nozzles are part of a blower tube extending over the entire width of the buckle plate.

Collecting pockets as described in European Patent Application EP 0 511 574 A1, corresponding to U.S. Pat. No. 5,246,415, for instance, are likewise known in the art. Such collecting pockets are used to collect a plurality of individual sheets. The collected sheets are then jointly moved out of the collecting pocket and fed to a downstream folding unit, allowing the collected sheets to be jointly folded.

It is also known to feed sheets to be folded to a folding unit in a shingled formation, i.e. in an overlapping formation, as disclosed, for instance, in German Patent Application DE 10 2008 048 286 A1, corresponding to U.S. Pat. No. 8,419,603 and German Patent Application DE 10 2008 048 287 A1, corresponding to U.S. Pat. No. 8,628,457. In that context, a particular difficulty lies in guiding the sheets as they enter and leave the folding units, especially the buckle plate.

A disadvantage of the aforementioned folding units is that in particular at high speeds, it is impossible to securely guide sheets through the folding unit and into a downstream folding unit. Damage to the sheet and undesired folds or post-folds may occur, for instance, as the fold is initiated, resulting in poor quality products.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a buckle folding unit and a sheet-fed folding machine including the buckle folding unit, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which have improved properties in terms of guiding sheet-shaped elements in the buckle folding unit.

With the foregoing and other objects in view there is provided, in accordance with the invention, a buckle folding unit for folding sheet-shaped elements, in particular sheets of paper, board, and plastic, which may be fed in shingled formation. The buckle folding unit includes a buckle plate and three rollers, with two of the rollers forming a transport roller pair for feeding the sheet-shaped elements and two further rollers forming a folding roller pair for folding the sheet-shaped elements, as well as at least one blown-air nozzle for guiding the sheet-shaped elements in the buckle folding unit. The blown-air nozzle is advantageously constructed and positioned in such a way that the at least one blown-air nozzle emits, i.e. provides a blown-air jet oriented in a direction that is radial to the common roller of the transport roller pair and the folding roller pair. The radial orientation of the blown-air jet means that the blown air is directed from the blown-air nozzle to the central axis of the entrance-side roller of the two folding rollers. Thus a sheet-shaped element is placed against the surface of that roller and is guided into the nip of the folding roller pair in a defined way, which may increase the quality of the fold.

In accordance with another preferred feature of the invention, the blown-air nozzle is assigned a control unit for activating the blown-air nozzle in a specific timed way. Thus the blown-air jet may be activated when or shortly before a leading edge of a respective sheet-shaped element rests against a leading-edge stop of the buckle plate.

In accordance with a further particularly advantageous and preferred feature of the buckle folding unit of the invention, the latter has a plurality of blown-air nozzles successively disposed in a nozzle bar, which extends approximately over the width of the buckle plate or folding rollers.

In accordance with an added feature of the buckle folding unit of the invention, the buckle plate is disposed at an angle of 20° to 40° relative to a plane of introduction of the sheet-shaped elements into the buckle folding unit. The plane of introduction represents the plane in which sheet-shaped elements are transported to the buckle plate by the transport roller pair and in which likewise the common tangent to both transport rollers is located. This configuration of the buckle plate at a flat angle promotes a better introduction of the sheets into the buckle plate.

In accordance with an additional particularly advantageous and thus preferred feature of the buckle folding unit of the invention, at least the further roller of the folding roller pair, i.e. not the entry-side folding roller but the plate-side folding roller, which is not part of the transport roller pair, is provided with at least one groove on its surface, in particular a circumferential groove, also referred to as a channel. The groove is formed as a depression in the surface of the roller. This allows the air that is present between the sheet-shaped element and the pair of folding rollers to escape faster and more easily during the folding process. This avoids a pressure build-up on one side of the sheet-shaped element, namely underneath the sheet-shaped element in the so-called folding space, resulting in an improved quality of the fold.

With the objects of the invention in view, there is concomitantly provided a sheet-fed folding machine including a buckle folding unit as described above.

A nozzle bar having blown-air nozzles as described above may also be used in a reversing device as described, for instance, in European Patent EP 1 925 579 B1.

As far as it makes sense from a technical point of view, combinations of the invention as described above and the advantageous further developments of the invention likewise form advantageous further developments of the invention.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a buckle folding unit and a sheet-fed folding machine including the buckle folding unit, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. Further advantages and embodiments of the invention that are advantageous in structural and functional terms will become apparent from the dependent claims and the description of exemplary embodiments with reference to the appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic, longitudinal-sectional view of a sheet-fed folding machine in accordance with the invention;

FIGS. 2A and 2B are front-elevational views of prior art buckle folding units;

FIG. 3 is a front-elevational view of a buckle folding unit in accordance with the invention; and

FIGS. 4A and 4B are respective front-elevational and top-plan views of another embodiment of a buckle folding unit in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in detail to the figures of the drawings which are not drawn to scale and in which components that correspond to one another have the same reference symbol, and first, particularly, to FIG. 1 thereof, there is seen a sheet-fed folding machine 100 including a sheet feeder 10, a feed unit 20 with an alignment table, a buckle folder 30 having two buckle folding units 30.1, 30.2, and a signature delivery 50. In the region of the sheet feeder 10, a respective sheet 1000 is separated from a sheet stack 1001 and transferred to the feed unit 20 having the alignment table. A respective sheet 1000 is fed from the feed unit 20 to the buckle folder 30 in a direction of sheet transport T. Upstream knife shafts 31 treating the sheets 1000 may be provided to prepare the folds. The actual treatment of the sheets 1000 is carried out in the buckle folding unit 30, i.e. the sheets 1000 are folded by a buckle plate 33 in cooperation with folding rollers 32. The construction of the buckle folding unit 30 will be described in more detail based on the further figures. A sheet 1000 that has been folded in the buckle folding unit 30 is delivered to the signature delivery 50 as a signature 1002.

FIGS. 2A and 2 b illustrate a buckle folding unit 30.1 in accordance with the prior art. Two rollers 32.1 and 32.2, which form a transport roller pair, transport a respective sheet 1000 in a direction of transport T into the buckle plate 33 until the leading edge of the sheet 1000 is in contact with a leading edge stop 34. As shown in FIG. 2B, the sheet 1000 then buckles in a folding space 36 and is gripped by a folding nip formed between the rollers 32.2 and 32.3, which form a folding roller pair. This is the actual folding process. The buckling process is dependent on a number of factors, for instance the traveling speed of the sheet, the weight of the sheet, the configuration of an entrance 35 to the buckle plate, the width of the sheets 1000, the surface of the rollers 32, etc.

In order to improve the quality of the fold, a nozzle bar 41 with a number of blown-air nozzles 40 is provided in the entrance or entry region 35 of the buckle plate 33, i.e. in the region of an upper plate edge. The blown-air nozzles 40 are aligned in such a way that they provide an air jet 42 that is oriented in a radial direction relative to the second roller 32.2, i.e. that is directed towards the central axis of the second roller 32.2. This air jet 42 causes a sheet 1000 to be reliably placed flatly against the second roller 32.2 and to be introduced into the nip of the folding roller pair 32.2, 32.3 in a defined way. In contrast, an air jet directed directly into the nip would not cause any increase in the accuracy of the fold. The initiation of the folding process in that case would be dominated by the air jet and the formation of the fold would not be precisely reproducible because a sheet would “flutter” into the nip of the folding roller pair more or less by chance. Due to the radial direction of the air jet 42 in accordance with the invention, the initiation of the folding process is very accurate and reproducible for every sheet 1000. In this case, the formation of the fold is substantially determined by the geometric dimensions of the folding unit 30.1, namely by the position of the stop 34.

In the embodiment shown in FIG. 3, the buckle plate 33 is oriented at an angle α of introduction of approximately 25° relative to a plane E of introduction. In contrast to the angles of introduction common in the prior art of approximately 45°, a sheet 1000 may enter the buckle plate 33 more easily and disruptions to the introduction process may be avoided.

The blown-air nozzles 40 may be integrated in the illustrated position into the nozzle bar 41 extending over the respective widths of the buckle plate 33 and of the folding rollers 32, as shown in FIG. 4B. As is additionally indicated in FIG. 4B, the nozzle bar 41 is connected to a blown-air source 44 and may be supplied with blown air in a timed way by a control unit 45 of the machine. For this purpose, a sensor with a data connection to the control unit of the machine may be integrated into the buckle folding unit 30.1 to monitor contact between the leading edge of a respective sheet 1000 and the buckle plate stop 34 and to provide a signal for the provision of blown air.

In the embodiment shown in FIG. 4A, at least one channel 37, also referred to as a groove, is formed in the surface of the buckle-side folding roller 32.3. The groove 37 is formed as a depression in the lateral surface of the folding roller 32.3 and is in particular an endless circumferential groove formed in the lateral surface of the roller 32.3. The groove 37 forms an air channel that helps the air that is present underneath a sheet 1000, i.e. between the sheet 1000 and the folding roller pair 32.2, 32.3, to escape. The presence of air is undesired in this location during the initiation of the folding process because it hinders close contact between the sheet 1000 and the folding rollers 32.2 and 32.3. Therefore, the air is allowed to escape not only on the bearing-side ends of the folding rollers 32.2, 32.3, but also through the channel 37. As is shown in the top view of FIG. 4B, a number of channels 37 are formed in the lateral surface of the folding roller 32.3. 

1. A buckle folding unit for sheet-shaped elements, the buckle folding unit comprising: a buckle plate; three rollers forming a transport roller pair for feeding the sheet-shaped elements and a folding roller pair for folding the sheet-shaped elements, one of said three rollers being a common roller of said transport roller pair and said folding roller pair; and at least one blown-air nozzle for guiding the sheet-shaped elements, said at least one blown-air nozzle delivering an air jet oriented in a radial direction relative to said common roller.
 2. The buckle folding unit according to claim 1, which further comprises a control unit associated with said blown-air nozzle for activating said blown-air nozzle in a timed manner.
 3. The buckle folding unit according to claim 1, which further comprises a nozzle bar, said at least one blown-air nozzle including a plurality of blown-air nozzles disposed in a row in said nozzle bar.
 4. The buckle folding unit according to claim 1, wherein the sheet-shaped elements are introduced to said buckle plate along a plane of introduction, and said buckle plate is disposed at an angle of introduction of approximately 20° to 40° relative to said plane of introduction.
 5. The buckle folding unit according to claim 1, wherein at least a further roller of said folding roller pair not being said common roller has a surface and at least one channel formed in said surface.
 6. The buckle folding unit according to claim 5, wherein said surface of said further roller is a lateral surface, and said at least one channel is an endless circumferential channel formed in said lateral surface.
 7. A sheet-fed folding machine, comprising: at least one buckle folding unit according to claim
 1. 